The present invention relates to an improved annular seal which can be used to seal across the annular space between well members. Difficulty has been encountered in the past with annular seals since manufacturing tolerances and deflection of components due to hoop strain creates an extrusion gap and adversely affects the ability to seal, the seal life and for elastomers causes extrusion problems.
Efforts have been made in prior seal assemblies to provide a structure in which the pressure to which the seal is exposed is utilized to cause a lip to move in the direction to provide a sealing engagement with a cylindrical surface against which the seal is to be provided.
The H. W. Millmine U.S. Pat. No. 2,007,501 discloses a packing for a pump rod which is rubber or similar material and includes an outer lip and an inner lip with a compression space between the lips. The fluid being pumped is received within the compression space and exerts a pressure against both lips to hold them in sealing engagement with the surfaces against which they are to seal. A plurality of channels through the packing connect the compression space with a recess on the interior of the packing to provide cooling for the reciprocating rod which moves within the packing. A filter is provided at the intersection of the duct and the compression space to prevent the entry of sand and sediment into the rod cooling recess.
The S. D. Gullion U.S. Pat. No. 4,742,874 discloses a subsea wellhead seal assembly for sealing between the interior of a wellhead housing and the exterior of a hanger. The seal assembly includes a U-shaped metal seal ring with a pair of interengaged annular wedging members which are forced into the interior of the U-shaped metal seal ring to cause its inner and outer legs to be spread apart into sealing engagement with the walls on the interior of the housing and the exterior of the hanger.
The T. G. Cassity U.S. Pat. No. 4,771,828 discloses a wellhead seal which includes an annular sealing member for sealing across the annular space between two wellhead members. The annular sealing member includes a plurality of inner and outer lips which are tapered in a direction toward the surface against which they are to seal and toward the pressure to which they may be exposed. The sealing surfaces of the wellhead members are prepared to provide an undercut on the sealing surfaces so that the pressure to which the seal is exposed can enter the undercut space and urge the undercut portion of the sealing surface in the direction toward the annular sealing member. In this manner the pressure being sealed urges both the seal lips on the annular sealing member and the undercut sealing surface portions toward each other to provide a positive seal.